Electric kiln



Patented May 2.19, 1928.

`orari-:D STATES .1,671,742 PATENT- Sori-lcs THEODORE C. PBOUTY AND WILLIS O. PROUTiY, F HERMOSA-BEACH, CALIFORNIA.

ELECTRIC' xILN.

Application led :lune 27,

Our invention is an improvement in elecy trically heated tunnel kilns and has for its principal object the disposition of the heating elementsin such manner as to apply the radiated heat to the ware being fired with minimum loss through the walls of the kiln. In order to accomplish this pur ose we mount the heating elements upon t ie movable platform. which carries the ware through the kiln and in close proximity to the ware whereby only a negligible amount of heat is radiated to the tunnelwalls. Substantially all of the radiant-energy is absorbed by the ware, the only heat conveyed to the tunnel walls being that carried there-v to by the heated air in the tunnel space. In the drawings:

Figure 1 is a transverse section of a tunnelf Figure 2 is afragmentary sectional viewon lane 2 2 Vof Figure 1.`

Iigure 3 is a fragmentary sectional view on plane 3-3 oFigure 1.

Figure 4' is a ,perspective view of one of the contact brushes carried by the heating elements.

We have illustrated the inventionas-apl plied to a kiln of the type shownA in Patent No. 1,613,054, granted January 4, 1927, but it may be adapted to tunnel ki ns employing cars or other means to move the ware.` The walls 1 of the kiln are constructed to prevent as far as possiblethe loss ofheat by conduction, and the inner surfaces of the walls will preferably be glazed to prevent transmission of radiant heat as described in co-pending application of Willis O. Prouty executed June 18, 1927. As described in the prior patent above referred to, the kiln'is provided with a floor 2 of vitrified refractory material, upon which rest and slide the plates 3,- suitablev means being provided, as described in said previous patent, to propel the plates through 'the tunnel.

At intervals narrow'plates 4, preferably lsomewhat thicker 'than plates 3 are placed between adjoining plates 3 toserve as bases l for the u right supports 5 upon whichthe heating e ements 6 arewou'nd orotherwise supported. It will be 'understood,lof course, that the heating elements 6 maybe con structed of any fof the resistance metals or alloys suitable for the purpose and that the other Yparts described are formed of suitable refractory material. We have shown the resistance wire 6 as wound .in helical form i927. Serial No. 201,809.

through perforations in the supporting plate 5, though other arrangements of the heating element upon itsvsupport might be elnployed. The outer edges of the Hoor of the tunnel are elevated as indicated at 9 and 10 forming guides .between which the plates 3, 4 move throughfthe center of the tunnel equidistant from the side walls. The plates vupon which the heating elements 6 are supported may. be inserted in grooves in the plates 4 as shown in` the drawing.

The conductors or'bus' wires forsupplying current to the heating elements 6 ,may be mounted in grooves extending longitudinally along the upper surfaces of the elevated floor-sections 9, 10. The opposite ends of each I'heating element fare outwardly turned as indicated at 7, 8 to overhang the bus wires 12, 1l, and carry brushes 14,` 15

which bear upon the bus wires. These brushes may take the form of strips bent at one end to embrace the overhanging end ofthe electrical element and at the other curved to drag smoothly over the bus wire as shown in Figure 4. A weight 15 may be placed upon 'each of the brushes to insure close contact with the underlying bus Wire.

As indicated in Figure 3` the bus wires may be indetached sections 11,-11, and the pairs of Wires in each section upon opposite sides of the kiln may be in separate circuits" carrying different voltages. As the conveyor units 8, 4- move throughthe kiln the brushes 14, 15 of each of the several heating elements will contact successively with the bus terminals of the several circuits and vby arranging the-successive Ycircuits with gradually rising voltages the ware may be properly preheated and gradually brou ht to the maximum firing temperature, anA it desired the cooling may be retarded by providing one or more following circuits carrying current 'at a lower potential.

We claim: Y

1. In a tunnel kiln, a conveyor for moving ware therethrough, electrical heating elements mountedA upon said conveyor, and means for supplying electric current to said elements while moving through said kiln.

2. In a tunnel kiln, a conveyor for moving ware therethrough, electrical heating elements mounted on said conveyor, electrical .contact members mounted in the tunnel space of the kiln and means forestablishgifi'ig,

contact between the terminals of said ,li/eatware therethrough, .electrical heating'I elex ments mounted on said conveyor, and a plu- 4. Ina tunnel kiln, a conveyor for moving rality of pairs of electrical contact. members mounted in and extending longitudinally of said kiln, and terminals upon said heating elements adapted to establish electrical connection successively with said pairs of con; v

tact members during the movement'of-said elements through'said tunnel.

In testimony whereof, we have Subscribed ournames.

i THEoDc'iRE o. PRoUTY'. WILLIS o. rRoUTY, i 

